1. Field of the Invention
The present invention relates to an aqueous ink, and an ink jet recording method, an ink cartridge, a recording unit and an ink jet recording apparatus using such an aqueous ink.
2. Description of the Related Art
An ink used in ink jet recording systems is required to be an ink giving a high image density (OD value) for the purpose of achieving high image quality. In addition, an ink, which prevents recording media from being stained even when recording is continuously conducted, i.e., has excellent fixing ability, is required for the purpose of achieving speeding-up.
Various techniques have been proposed to date for the purpose of enhancing the image density. For example, they include a technique of using a coloring material excellent in color developability and a technique of composing the composition of an ink to enhance the associated state or aggregating ability of a coloring material, thereby leaving a greater amount of the coloring material on the surface of a recording medium.
There is a proposal of paying attention to the dynamic surface tension of an ink as a technique for controlling permeation of the ink into a recording medium or blurring of the ink. For example, Japanese Patent Registration No. 2516218 (Patent Document 1) has proposed the provision of an ink excellent in drying ability by controlling [dynamic surface tension (dyn/cm) at a life time of 0 millisecond+viscosity (cp)] within a range of from 42 to 49. Japanese Patent Application Laid-Open No. 2003-238851 (Patent Document 2) has proposed the provision of an ink of which the maximum value of the rate of change of the dynamic surface tension is from 0.2 mN/m/s to 0.4 mN/m/s. Japanese Patent Application Laid-Open No. 2005-200566 (Patent Document 3) has proposed the provision of an ink having a dynamic surface tension of from 25 to 50 mN/m at a lifetime of 10 milliseconds, in which the difference between the maximum value and the minimum value of the dynamic surface tension is 5 mN/m or less. Japanese Patent Application Laid-Open No. 2003-231838 (Patent Document 4) has proposed the provision of an ink having a dry viscosity of 100 mPa·s or less, a dynamic surface tension of at least 45 mN/m in the lifetime of 10 milliseconds and a dynamic surface tension of 35 mN/m or less at a lifetime of 1,000 milliseconds.